Redox-Triggered Buoyancy and Size Modulation of a Dynamic Covalent Gel

Abstract

The development of stimuli-responsive materials capable of transducing external stimuli into mechanical and physical changes has always been an intriguing challenge and an inspiration for scientists. Several stimuli-responsive gels have been developed and applied to biomimetic actuators or artificial muscles. Redox-active actuators in which the mechanical motion is driven chemically or electrochemically have attracted much interest, and their actuation mechanism is based on the change in electrostatic repulsion and the loss or gain of counterions to balance newly formed charges. Actuation can also be promoted by changing the hydration state of the material, leading to the release/adsorption of water molecules from the network, inducing a direct shrinking/swelling of the material, respectively. A cationic crystalline dynamic covalent gel was obtained via the formation of imine bonds between 2,6-diformyl pyridine and triamino guanidinium chloride. The gel exhibits a reversible contraction/expansion behavior...